The PCCS (Practical Color Co-ordinate System) has heretofore been widely known as a color system for use in color design conscious of color harmony. FIG. 36 is a conceptual diagram for explaining the concept of the PCCS.
The PCCS defines a concept “tone” which can be said to be a composite concept of lightness and saturation, and expresses a basic series of color harmony by two series “hue” and “tone.” In the PCCS, 12 types of tones or concepts expressing color tones are defined, including “soft (sf),” “pale (p),” and “strong (s).”
Colors belonging to the same tone series have common emotional effects (impressions) even in different hues.
As described above, “tone” is a concept of color perception having a certain perceptual regularity. However, its correlation with a psychophysical value which is a quantity obtained by evaluating the strength of a stimulus, a physical quantity, in terms of the strength of a sensed quantity is unknown. The psychophysical value of color belonging to an arbitrarily defined tone is therefore unable to be determined.
Creating a color chart of arbitrary intermediate tones and the like not defined on the PCCS (such as intermediate tones between “pale (p)” and “light (lt)”) therefore needs to rely on trial and error based on human perception. Manual operations based on human perception can easily cause variations depending on the sense of the creator.